1. Field of the Invention
The present invention relates to an inkjet type image forming apparatus for forming images on a sheet by jetting ink droplets from an inkjet head (hereinafter, also abbreviated as ink head).
2. Description of the Related Art
In recent years, inkjet type image forming apparatuses have been proposed, such as those described in patent documents 1 and 2. Patent document 1 describes an image forming apparatus including plural image forming units connected to each other. Each of the image forming units includes an inkjet engine for jetting ink droplets, which is removably attached to the image forming unit.
Patent document 2 describes an inkjet print system in which plural inkjet print units are disposed at predetermined intervals along a direction of conveying a continuous sheet, so that plural colors can be printed onto both sides of the continuous sheet. The inkjet print system detects marks formed along the continuous sheet, and starts the printing operation performed by the inkjet print units based on detection signals.
FIG. 18 is a schematic diagram of the image forming apparatus described in patent document 1, FIG. 19 is a perspective view of an image forming unit included in the image forming apparatus shown in FIG. 18, and FIG. 20 is a perspective view of an inkjet engine installed in the image forming unit shown in FIG. 19.
The image forming apparatus shown in FIG. 19 includes two image forming units 101A and 101B having substantially the same configuration, which are connected to each other. Each of the image forming units 101A and 101B includes an inkjet engine 102, a sheet feeding cassette 103, a supply conveying path 104 for supplying a recording sheet S in the sheet feeding cassette 103 to the inkjet engine 102, and an eject conveying path 105 for conveying the recording sheet S on which an image has been formed out from the inkjet engine 102.
As shown in FIG. 19, each of the image forming units 101A and 101B have a substantially cubical shape. A conveying inlet 106 for the recording sheet S is formed on one side of the image forming unit 101B, and a conveying outlet (not shown) for the recording sheet 5 is formed on the other side of the image forming unit 101B.
As shown in FIG. 18, an inkjet engine attachment part 107 is provided between the supply conveying path 104 and the eject conveying path 105. The inkjet engine 102 can be removably attached to the inkjet engine attachment part 107 (see FIG. 19). On one side of the inkjet engine 102, there are provided ink cassettes 108 for separately storing yellow (Y), magenta (M), cyan (C), and black (K) ink. The ink cassettes 108 and the inkjet engine 102 are connected by an ink supplying path 109 (see FIG. 18).
As shown in FIG. 20, the inkjet engine 102 includes a carriage 110, a driving motor 111 for moving the carriage 110 in a main scanning direction, a conveying belt 112 for conveying the recording sheet S, and conveying rollers 113.
The carriage 110 includes ink heads (not shown) each having multiple jetting outlets on the bottom side, for the colors of yellow (Y), magenta (M), cyan (C), and black (K). The conveying belt 112 is rotated/driven by a driving motor 114.
For example, in FIG. 18, the image forming unit 101A is used to print line images, and the image forming unit 101B located on the downstream side of the image forming unit 101A is used to print character images, so that a complete image can be formed. In this manner, the printing operation can be divided between the image forming units 101A and 101B. Therefore, the printing operation can be accelerated and the degree of freedom in forming images can be enhanced.    Patent Document 1: Japanese Laid-Open Patent Application No. 2008-221500    Patent Document 2: Japanese Patent No. 2979393
In the market of inkjet printers, there is increasing demand for high printing speed, highly precise images, and high image quality, and this demand is made for various types (specifications) of printers. In order to manufacture different machine types to address each of the specifications, complex manufacturing operations and increased development costs for the different machine types will be required. In recent years, there is demand for an image forming apparatus in which functions can be easily expanded or changed. Furthermore, with the increase of printing speed, reduction of the machine downtime has been an issue.
In the image forming apparatus illustrated in FIGS. 18 through 20, units such as the inkjet engine 102, the sheet feeding cassette 103, the supply conveying path 104, and the eject conveying path 105 are incorporated into a single body in each of the image forming units 101. Thus, when considering the various specifications of the image forming apparatus as in the present invention described below, none of the units can be shared by other units in this image forming apparatus. For this reason, the functions cannot be easily expanded or changed.